A new survey of likely Iowa caucusgoers shows Mitt Romney leading the Republican presidential field with support from 21 percent of those contacted.

Michele Bachmann, who has made Iowa the major focus of her campaign, polled second at 15 percent, followed by Rick Perry at 14 percent and Ron Paul at 12 percent. Fifteen percent of those surveyed were undecided.

Those results vary significantly from other recent surveys of Iowa voters, which generally have placed Perry atop the field and Romney further back.

A Real Clear Politics average of three Iowa surveys from mid-to-late August shows Perry leading with 24.7 percent, followed by Bachmann at 18.3 percent and Romney at 18 percent.

The American Research Group survey released Wednesday reached 600 likely Republican caucus attendees by phone between Sept. 22 and 27. Its margin of error was 4 percent. See the data here.

The survey registers support for Sarah Palin at 4 percent. Palin has not declared her candidacy and has been included in presidential preference polls only intermittently in recent months.

Romney’s support is up — and Perry’s is way up — from ARG’s previous poll, while Bachmann’s has dropped significantly.

A July survey from the same firm showed Bachmann leading at 21 percent, followed by Romney at 18 percent. Perry, who had not yet entered the race, polled at 2 percent.

Romney’s support comes despite minimal campaigning in Iowa. The former Massachusetts governor has held just 12 events in the state since January, 2008.

Bachmann, by contrast, has called Iowa critical to her campaign and visited often. Perry has already visited Iowa more than Romney, despite joining the race only last month.

The most recent Des Moines Register Iowa Poll, from June, had Romney leading with 23 percent, followed closely by Bachmann at 22 percent (although when the survey was taken she had not formally opened her campaign). Perry was not included in the Iowa Poll, nor was Palin.

The ARG survey released today also breaks out candidates’ support among likely voters aligned with the conservative tea party movement. Among these voters, Bachmann ran first with support from 19 percent, followed by Perry (14 percent), Paul (13 percent) and the undecideds (14 percent). Romney won support from just 6 percent of tea party voters.

While Romney was weak with the tea party, he did poll better than the field among “definite” caucus participants. Romney won support from 19 percent of definite attendees, while supporters of Bachmann, Perry, Paul and the undecideds were bunched at 15 and 14 percent.